The first scope cart was the Type 500 designed for the 517 oscilloscope which had an external power supply. We have a Type 500A Scope-mobile display at the museum with a 541 oscilloscope.
Here is an interesting dual version of the Type 500A Scope-mobile
This TekTalk July 1953 issue discusses the first Scope-mobile.
Gale Morris was hired in 1958 and asked to do a new Scope-mobile design and came up with the Type 200. We have a number of Type 200 Scope-mobiles on display at the museum including this one with a Type 7704 oscilloscope. There is additional information of the 200 Scope-mobile on the Gale Morris employee page.
Howard Vollum is shown here along with a Scope-mobile at Wescon in the mid 1960s.
These are a number of publicity photos for the various Scope-mobiles.